ES2963386T3 - Procedure and installation for a water treatment process - Google Patents

Abstract

A method for treating process water from a flotation plant is disclosed (1). The flotation plant (1) comprises a mineral float line (10) and a process water circuit (20) to treat underflow and/or overflow from the float line. The process water circuit comprises a gravitational solid-liquid separator (21) to dewater the underflow and/or mineral waterline overflow to separate the sediment (212) from the supernatant (211) comprising at least water. and unrecovered fine particles comprising valuable material; and a water recovery tank (25) to collect process water (500). According to the method, before leading the supernatant (211) from the gravitational solid-liquid separator (21) to the water recovery tank (25), it is subjected to cleaning flotation, in which at least 90% of the bubbles of flotation gas have a size of 0.2 to 250 μm, in a cleaning flotation unit (23). Also disclosed is a provision for treating process water from a flotation plant and its use. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Procedure and installation for a water treatment process

TECHNICAL SECTOR

The present invention relates to a procedure and an installation for a water treatment process of a flotation plant, and to the use of the installation.

STATE OF THE PRIOR ART

The quality of mineral ores decreases as the best deposits are increasingly used or have already been used. Therefore, the mined ores may contain considerably less valuable material. In order to carry out profitable exploitation, it is necessary to release all valuable metals or various valuable materials from the deposits.

When valuable minerals are deposited in smaller cavities within a parent rock, the need arises to crush the ore to finer levels, usually to an average particle size of less than 300 pm, and where a circuit is used of re-grinding, even of less than 100 pm, in order to release valuable material from the less valuable or worthless matrix, before treating the particles containing valuable material in a concentration process, such as flotation in a plant of flotation. When minerals are ground to a finer particle size, the amount of fine particles naturally increases, that is, particles that have an average particle size less than 10 pm. Fine particles disturb the main flotation process, for example by consuming an excessive amount of flotation chemicals. The ordinary dispersion processes of air flotation, pneumatic flotation or column flotation are not very efficient in recovering fine and light particles due to the size of the flotation gas bubbles of these flotation processes. For example, foam flotation employs a range of bubble sizes between 600 and 2500 pm, selected to create sufficient buoyancy for relatively large, raw ore particles having a particle size greater than 100 pm.

Removal of unwanted fines is carried out by removing slurry from the main ore stream in a classification circuit, the reject fraction of which is usually subjected to solid-liquid separation by gravity in a slurry thickener. However, the fine particle fraction may comprise a significant amount of valuable material that is lost if reject streams or unwanted material streams are simply disposed of as waste. In some cases, the amount of valuable material in the fines fraction may be between 10 and 30% and therefore it would be very important to also recover this material to increase the economic viability of an enrichment operation.

Typically, gangue, tailings or slop materials comprising unwanted or worthless material removed in a flotation process are sent to a tailings impoundment where the long residence time, typically 20 to 40 days, is expected to settle. and separate solids, as well as decompose residual chemicals from flotation of collected and reusable process water. The collected process water is then recirculated back to the enrichment process.

Before taking the aforementioned fractions to a waste impoundment, the material streams can be dewatered in various types of solid-liquid gravity separators such as thickening agents, from which the overflow or supernatant material is recirculated to the main process. of flotation. From a classification circuit, the unwanted material fraction may be subjected to dewatering in a sludge thickener, and the fraction intended for the subsequent flotation stage(s) may be subjected to dewatering and/or conditioning in a flotation thickener. . Overflow water or overflow material is also collected, stored in recovery water tanks and recirculated back into the flotation process to be used in various applications, such as dilution water for grinding or conditioning.

Depending on the type of ore treated in a flotation plant, overflow water or supernatant material, or process water from those sources, can comprise a significant amount of valuable material in the form of fine particles. Additionally, the water may comprise residual flotation chemicals, other fine particles such as silicate-containing particles, colloidal and soluble compounds, and microbes and/or compounds that promote microbiological growth. In general, this type of recirculated process water collected from various points in the flotation plant is not suitable for recirculation back into the flotation process, but more significantly, it may comprise a considerable amount of valuable material in the form of Fine particles carried over from main waterline operations.

Nowadays, water scarcity, ecological demands imposed by legislation and public pressure, costs and large space requirements of the above-mentioned conventional rewashing procedures for the treatment of process waters are putting increasing pressure to recirculate process waters, so that the main processes in flotation become, at least partially, closed loop systems in terms of water utilization. Alternative procedures for the treatment of tailwater flows may be necessary, allowing at least partially closed loop water systems. Examples of such systems are shown in Patents US3622087 and US3782539.

A conventional tailings treatment procedure with a normal residence time of between 20 and 40 days can result in acceptable water quality, allowing the treated process water to be reused in the main flotation process, and in other stages of the process. Switching to other rewashing procedures, such as thicker rewashes, paste, dry stacking or hybrids thereof, will result in a much shorter settling time, due to the new thickeners required at these stages of the process. The shortest settling times, approximately 3 to 8 hours, or even shorter in cases where settling is used as a washing step to separate the coarse particle fraction (solids) from the fine particle fraction (solids). liquid), resulting in more fines, residual chemicals and other harmful or harmful substances that end up overflowing from the thickening agent and then into the recycling or recirculation process water. In addition to comprising a considerable fraction of fine particles with valuable material, these impurities in the recirculated process water can negatively affect the main flotation process and the quality of the final product, if not handled properly before recycling the process water again. in the main process. In general, closed water systems cause problems in the operability of the flotation process and increase disturbances, which makes controlling the flotation process more difficult.

Increased fines in thickener overflows may require increased flotation chemical dosage or decreased recovery and quality of the desired valuable material. The fines loading may also increase due to the need to further pulverize the low quality ore material by grinding it to a smaller particle size, in order to get the ore into a form that allows recovery of the valuable material. The accumulation of fines, as well as impurities such as microbes and organic matter, negatively affects subsequent dehydration. Fine materials, especially those of silicate origin, alter the ability of harvesting chemicals to act as intended, because silica-containing fines may have opposite surface potentials and may therefore adhere to mineral surfaces and produce a steric effect that prevents the collectors from adhering to the particles or a steric layer so thick that the length of the collector molecule is not sufficient to make the ore particles hydrophobic - the apparent surface energy remains unchanged and Binding to flotation gas bubbles cannot occur. Additionally, fines that comprise only unwanted material are more difficult to press into the slop/waste. The selectivity of the reagents decreases as the amount of fines increases. Fines in the form of compounds such as colloidal hydroxides and carbonates present in the flotation circuit can combine and produce large surface areas that react with and consume the flotation chemicals.

Switching to other rewashing procedures, such as thicker rewashes, paste, dry stacking or hybrids thereof, will result in a much shorter settling time, due to the new thickeners required at these stages of the process. This leads to a much shorter settling time, ranging from 3 to 8 hours, resulting in more fines, residual chemicals and other harmful or deleterious substances ending up in the thickener overflow and then into the process water. recycled. Chemicals and other compounds accumulate in a closed loop of water, since these substances cannot be efficiently removed by standard dewatering operations. Thus, for example, thickener overflow will comprise material that is difficult to settle and residual chemicals that will negatively affect the main flotation process. These must be removed from the overflow if the process water is to be recirculated without causing problems in the main processes due to residual flotation chemicals, etc., carried over from dewatering. Fines can pose a problem, especially since this type of system does not reduce fines effectively due to the relatively short residence time. Likewise, microbiological contaminants can cause problems.

CHARACTERISTICS OF THE INVENTION

The method according to the present invention is characterized by what is presented in claim 1. The installation according to the present invention is characterized by what is presented in claim 23. The use of the installation according to the present invention is characterized by what is presented in claim 33.

A procedure is disclosed to treat the process water of a flotation plant for the recovery of a valuable material. The flotation plant comprises a mineral flotation line comprising a crushing mill; a classification circuit, to classify the mill crushed ore feed into the overflow classifier and the settling classifier; and an ore flotation circuit, for treating the overflow of the classifier as a feed of ore particles comprising valuable material suspended in the slurry, the flotation circuit comprising a raw portion for separation of the slurry feed at an overflow raw of recovered valuable material and a reject raw decantation, and a cleaner part arranged to receive the raw overflow of the rawer part as a sludge feed, for separation of the sludge into a cleaner overflow of material valuable recovered and a cleaner decantation ready to flow again in the rawest part as a sludge feed. The flotation plant further comprises a process water circuit to treat the settling and/or overflow of the mineral float line, the process water circuit comprising a solid-liquid gravity separator to dehydrate the settling and /or mineral waterline overtopping, to separate the sediment from the supernatant comprising at least water and unrecovered fine particles containing valuable material; and a recovery water tank, to collect water from the process that includes overflow and/or decanting of the mineral waterline. The procedure is characterized in that, before taking the supernatant from the solid-liquid separator by gravity to the recovery water tank, the supernatant is subjected to a washing flotation, in which at least 90% of the gas bubbles of flotation have a size between 0.2 and 250 pm, in a flotation cleaning unit to collect at least fine unrecovered particles containing valuable material; to separate fine particles containing valuable material from the supernatant at the overflow of the cleaning flotation as recovered valuable material; and to obtain purified process water as decanted from the washing flotation; and, in that process, the purified water is recirculated to the mineral waterline or collected in the recovery water tank as collected process water.

In another aspect of the invention, an installation is disclosed for treating process water from a flotation plant for the recovery of a valuable material. The flotation plant comprises an ore flotation line comprising a crushing mill; a classification circuit, for classifying the ground ore feed from the crushing mill into an overflow classifier and a decanting classifier; and a mineral flotation circuit, for treating ore particles containing valuable material suspended in the slurry, the flotation circuit comprising a coarser portion for separation of the slurry feed into a coarser overflow of material. recovered valuable material and a raw decant of the reject, and a cleaner part arranged to receive the raw overflow of the rawer part as a sludge feed, for separation of the sludge into a cleaner overflow of recovered valuable material and a cleaner decant arranged to flow back to the cruder part as sludge feed. The flotation plant also comprises a process water circuit, to treat the settling and/or overflow of the mineral flotation line, the process water treatment circuit comprising a solid-liquid gravity separator arranged to dewatering the slop and/or mineral waterline overflow to separate the sediment from the supernatant comprising at least water and unrecovered fine particles containing valuable material; and a recovery water tank, to collect water from the process that includes overflow and/or decanting of the mineral waterline. The installation is characterized in that the water treatment circuit also includes a washing flotation unit, which uses bubbles of the flotation gas, of which at least 90% have a size between 0.2 and 250 pm. , operatively connected to the solid-liquid separator by gravity to receive the supernatant before its introduction into the recovery water tank, and arranged to collect at least unrecovered fine particles comprising valuable material; to separate fine particles containing valuable material from the supernatant in the wash flotation overflow as recovered valuable material; and to obtain purified process water as slop from the wash flotation configured to be recirculated to the mineral float line or collected in the recovery water tank as collected process water.

In yet another aspect of the invention, the use of the installation for treating the process water of a flotation plant for the recovery of a valuable material is disclosed, in which the installation is used to recover valuable material from an ore. which has a density of less than 4 g/cm3, preferably between 2.4 and 3.2 g/cm3.

With the invention, the aforementioned problems in water recirculation, and the inconveniences associated with conventional solutions, can be alleviated. The overflow or supernatant from a gravity solid-liquid separator is subjected to wash flotation in a wash flotation unit, so that fine particles, especially those comprising valuable material, can 1) float and be collected in the wash flotation overflow – collector chemicals carried over by the main flotation processes can act as collectors for fine particles, or additional chemicals can be used to further improve collection efficiency, 2) be separated of the process water thus purified by the washing flotation stage, and 3) be collected for further treatment as concentrate, thus increasing the overall recovery rate of the flotation plant. In some cases, for example, an overflow or supernatant of a sludge removal thickener may comprise up to 40% valuable material, which would be lost if it were not collected in the washing and flotation stage or unit.

Especially in connection with easily crushed ores, i.e. ores or minerals of relatively low density, such as spodumene (lithium aluminum inosilicate, LiAl(SiO<3>)<2>) or PGM minerals (mineral group of platinum), a significant amount of fines is created in the grinding circuit and, furthermore, in a new grinding circuit. Usually, these fines are eliminated from the crushed material destined to float in a classifying circuit, especially in cyclones that classify the ground material into accepted or overflow destined for the flotation process and rejected or decanted the particles that are too fine. To remove fine particles from the classifier decant, a sludge removal thickener is used to obtain fines-free process water for later use.

As explained above, the fine particle fraction may comprise a significant amount of valuable material, for example lithium or platinum. By recovering that fraction of fine material, instead of eventually losing the fine particles and the valuable material they contain in the waste impoundment or recirculating them back to the main waterline where they again probably end up settling and can also disturb flotation process, the overall recovery of valuable material can be increased with the invention.

Additionally, the resulting purified process water can be easily recirculated back to the main flotation process. Since purified process water contains significantly less residual flotation chemicals and fine particles, it may not negatively affect the primary flotation process.

Since the ore overflow or main flotation process remains for a relatively short time in the solid-liquid gravity separator, the flotation chemicals, collectors entrained in the overflow of the main flotation process, do not decompose, as would occur over time in a conventional waste impoundment. These collector chemicals can later be used in the washing and flotation stage as collectors, thus making possible the flotation and collection of the desired material, that is, the collection of fine particles, resulting in purified process water. . At the same time, these residual flotation chemicals are depleted and do not return to the main mineral flotation process when the purified water from the process is recirculated. Therefore, the main flotation process is not affected by such unwanted flotation chemicals, making the control of the mineral flotation process easier.

In the washing flotation process, other colloidal materials such as C, P, N, present in very fine particles, as well as any starch-based depressant reagent present in the process water can also be removed, thereby removing nutrients. that would favor microbiological growth in the purified process water. This can improve the outcome of any subsequent water treatment steps, such as filtration. For example, removing such material can prevent blocking of the filter holes of ceramic filters.

Since the sludge or gravity solid-liquid overflow separator comprises only fine particles (larger particles end up in the sediment), scrubbing flotation can be used energy-efficiently at the stage in which which is more effective, that is, to eliminate fine particles.

In one embodiment of the procedure, the process water circuit comprises a first solid-liquid gravity separator, to dehydrate the classifier sludge to separate the first sediment from the supernatant comprising at least water and unrecovered fine particles containing valuable material; a first sediment, arranged to flow into the filter circuit for the recovery of valuable material and supernatant collected in the recovery water tank as collected process water.

In a further embodiment, before taking the supernatant from the first solid-liquid gravity separator to the recovery water tank, the supernatant is subjected to a wash flotation, in which at least 90% of the gas bubbles of flotation have a size between 0.2 and 250 pm, in a first washing flotation unit to collect at least unrecovered fine particles containing valuable material; to separate fine particles containing valuable material from the supernatant in the washing flotation overflow as recovered valuable material; and to obtain purified process water as decanted from the washing flotation; and, in this process, the purified water is recirculated to the mineral waterline or collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a second gravity solid-liquid separator to dewater the classifier overflow to separate the second sediment from the supernatant comprising at least water and unrecovered fine particles containing valuable material; the second sediment conducted to the mineral flotation circuit as mud feed; and the supernatant collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a third solid-liquid gravity separator, to dewater the cleaner overflow of the flotation circuit to separate the third sediment from the supernatant comprising at least water and unrecovered fine particles containing material. valuable; a supernatant collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a fourth solid-liquid gravity separator, to dewater the raw slop from the flotation circuit to separate the fourth sediment from the supernatant comprising at least water and unrecovered fine particles containing material. valuable; a supernatant collected in the recovery water tank as collected process water.

In one embodiment, prior to recirculating the collected process water from the recovery water tank to the mineral float line, the collected process water is subjected to a wash flotation, in which at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a second washing flotation unit, to collect at least unrecovered fine particles containing valuable material, to separate fine particles containing valuable material from the process water collected in the wash flotation overflow as recovered valuable material and to obtain purified process water as decantation of the wash flotation; and, in that process, the purified water is recirculated to the mineral waterline.

Depending on the waterline configuration, the process water circuit may comprise several solid-liquid gravity separators configured to treat overflows and/or slops from various sources in the waterline. The supernatant(s) thereof may then be treated in the wash flotation as necessary, to recover fine particles containing valuable material, in order to improve the overall recovery of valuable material from the flotation plant. In a specific embodiment, the decantation of the classification circuit is taken, through a solid-liquid separator by gravity, to a washing flotation stage, to guarantee the recovery of fine particles containing valuable material from the classification circuit that can often comprise a significant amount of said fine particles.

In one embodiment, before conveying the overflow and/or decant from the mineral waterline to a solid-liquid gravity separator, the concentration of the overflow and/or decant is adjusted to between 0.5 and 15 % in weigh.

In a further embodiment, the turbulent flow of overflow and/or settling from the waterline of minerals are adjusted to a laminar flow as they are conveyed to the solid-liquid separator by gravity.

In one embodiment, at least 40% of the fine particles containing valuable material, not recovered in the ore waterline, are recovered from the supernatant of a solid-liquid gravity separator.

In one embodiment, the residence time of the mineral waterline overflow and/or decantation in the solid-liquid gravity separator is less than 10 hours, preferably between 0.5 and 8 hours.

A relatively short residence time means that the flotation chemicals, specifically the collector chemicals, do not decompose, but are carried away with the supernatant, and can be used in the next washing and flotation step. At the same time, the fine particles do not have time to descend to form a sediment, which would happen over time in relatively low-turbulence gravity solid-liquid separators. Adjusting the decant and/or waterline overflow flow to exhibit a laminar flow pattern can improve the separation or washing of fine particles from the particles that descend to form a sludge, resulting in higher solids content. desired in the sediment, and the amount of solid waste to be treated can be reduced.

In one embodiment, before taking the supernatant from a solid-liquid gravity separator to the wash flotation, the supernatant is conveyed to an overflow tank of the separator.

A separator overflow tank may be used to control the flow of supernatant to the washing flotation unit, or to a mixing unit if such a unit is used. This can help stabilize the overall process water treatment operation by controlling the flow of supernatant in subsequent operational stages.

In one embodiment, before leading the supernatant from a solid-liquid gravity separator to the washing flotation, the supernatant is led to a mixing unit to chemically condition it by adding a coagulant and/or a flocculant to flocculate at least the fine particles. which comprise valuable material in the supernatant.

In a further embodiment, the coagulant is chosen from a group comprising: inorganic scavenger, aluminum salts, iron salts and organic coagulants.

In yet another embodiment, a coagulant is added to the supernatant in an amount between 1 and 2,000 ppm.

In one embodiment, the flocculant is chosen from a group comprising: natural polymers, synthetic flocculants.

In a further embodiment, a flocculant is added to the supernatant in an amount between 1 and 100 ppm.

While there are normally sufficient flotation chemicals (collector chemicals) present as carryovers from the main flotation process in the supernatant, in some cases, it may be necessary to condition the supernatant prior to the wash flotation treatment, to ensure that sufficient fine particles are present. containing valuable material can be removed by the flotation washing unit. This can be carried out in a conventional mixing unit, configured to allow the addition of different chemicals, such as flocculants and/or coagulants, and the treatment of the fluid with these chemicals. The amount of coagulant and/or flocculant is chosen based on the process, and depends largely on the cost of the chemicals. Organic coagulants are more expensive than inorganic ones. Typically, flocculants are added in amounts less than 10 ppm.

In one embodiment, the temperature of the supernatant was adjusted to between 2 and 60°C before being conveyed to a washing flotation unit.

In one embodiment, the pH of the supernatant is adjusted between 6 and 12 before being taken to a washing flotation unit.

The temperature and/or pH of the supernatant may be inherent, i.e. caused by the preceding process steps or environment, or, as desired, the properties may be adjusted as necessary, for example to optimize wash flotation. .

In one embodiment, the scrubbing flotation unit is a Dissolved Gas Flotation (DAF) unit.

DAF is a microflotation process that is used in various applications in water or effluent clarification. The solid particles are separated from the liquid by using very small bubbles of a flotation gas, microbubbles. Microbubbles with a size range of 30 to 100 μm are generated by dissolving air or other flotation gas into the liquid under pressure. Bubbles form in a pressure drop when the dispersion is released. The solid particles adhere to the bubbles and rise to the surface. The floating sludge formed is removed from the liquid surface by DAF overflow sludge rollers. Sometimes chemicals may be necessary to aid flocculation and increase the effectiveness of solids removal. Colloid removal is usually possible with efficient coagulation.

In one embodiment, the valid material is Li.

In one embodiment, the valid material is Pt.

In one embodiment of the installation, the process water circuit comprises a first solid-liquid gravity separator, arranged to dewater the classifier decant to separate the first sediment from the supernatant comprising at least water and unrecovered fine particles containing material. valuable; the first sediment being arranged to flow into the filtration circuit for recovery of valuable material, and the supernatant being configured to be collected in the recovery water tank as collected process water.

In a further embodiment, the water treatment circuit comprises a first washing flotation unit employing flotation gas bubbles, at least 90% of which have a size between 0.2 and 250 pm, operatively connected to the first solid-liquid gravity separator to receive the supernatant, and arranged to collect at least unrecovered fine particles containing valuable material; separating fine particles containing valuable material from the supernatant at the overflow of the washing flotation as recovered valuable material; and obtain purified process water as decanted from the wash flotation, configured to be recirculated to the mineral float line, or collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a second solid-liquid gravity separator, arranged to dewater the classifier overflow to separate the second sediment from the supernatant, which comprises at least water and unrecovered fine particles containing valuable material; the second sediment being arranged to flow into the mineral flotation circuit as a sludge feed and the supernatant being configured to be collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a third solid-liquid gravity separator, arranged to dewater the cleaner overflow of the mineral flotation circuit to separate the third sediment from the supernatant comprising at least water and unrecovered fine particles. that contain valuable material; the supernatant being configured to be collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit comprises a fourth solid-liquid gravity separator, arranged to dehydrate the raw slop from the mineral flotation circuit, to separate the fourth sediment from the supernatant comprising at least water and non-fine particles. recovered containing valuable material; the supernatant being configured to be collected in the recovery water tank as collected process water.

In one embodiment, the process water circuit further comprises a second washing flotation unit employing flotation gas bubbles of which at least 90% have a size between 0.2 and 250 pm, operatively connected to the recovery water tank to receive the collected process water, and arranged to collect at least unrecovered fine particles containing valuable material, separate fine particles containing valuable material from the process water collected in the wash flotation overflow as valuable material recovered and obtain purified process water as decanted from washing flotation; the purified process water being arranged to be recirculated to the mineral waterline.

In one embodiment, the process water circuit comprises a separator overflow tank, in which the supernatant of a solid-liquid gravity separator is configured to flow before being conveyed to the washing flotation.

In one embodiment, the process water circuit further comprises a mixing unit, in which the supernatant of a solid-liquid gravity separator is arranged to flow before being conveyed to the washing flotation, the unit being arranged mixing process to chemically condition the supernatant to flocculate at least fine particles containing valuable material in the supernatant. In one embodiment, the cleaning flotation unit is a dissolved gas flotation (DAF) unit. In one embodiment of the use, the facility is used to recover Li.

In one embodiment, the facility is used to recover Li from spodumene.

In one embodiment, the facility is used to recover Pt.

In one embodiment, the facility is used to recover Pt from a PGM mineral.

The objective of the process and installation according to the present invention is to remove as much fine particles as possible from the settling and/or mineral waterline overflow. At the same time, as a side effect, residual flotation chemicals are consumed and eliminated. In this way, valuable material can be recovered from the fine particles and improve the overall recovery rate of the waterline. Additionally, since fine particles and residual chemicals left in the purified process water are detrimental to the primary flotation process and can decrease the quality and value of the final product (valuable metals/minerals), the problems associated with Recirculation of process waters back to the main flotation process can be alleviated. Both cases also decrease the efficiency of mineral flotation processes. Removing excess fines and residual flotation chemicals can decrease the consumption of new flotation chemicals and fresh water.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a greater understanding of the current invention and which constitute a part of this specification, show embodiments of the invention and, together with the description, help to explain the principles of the current invention. In the drawings:

Figures 1 to 3 are simplified presentations of flotation installations in which embodiments of the method according to the invention can be used.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the present invention, an example of which is shown in the accompanying drawings.

The following description discloses some embodiments in such detail that a person skilled in the art can use the flotation installation and its use, and the method based on the invention. Not all steps of the embodiments are explained in detail, since many of the steps will be obvious to the person skilled in the art based on this invention.

For reasons of simplicity, in the following embodiments the element numbers are kept in the case of repeating components.

The attached figures 1 to 3 show schematically a flotation plant 1. The figures are not drawn to scale and many of the components are omitted, for clarity. Some of the components are presented as boxes that represent a complete process.

The embodiments described above can be used in any combination with each other. Several of the embodiments may be combined with each other to form a further embodiment. A flotation cell to which the invention relates may comprise at least one of the embodiments described above. Therefore, the invention and its embodiments are not limited to the examples described above; On the contrary, they may vary within the scope of the claims.

The flotation plant 1 comprises a mineral flotation line 10. A crushing mill 11 is arranged on the mineral waterline 10, in which raw ore material, for example, spodumene, is ground to a suitable particle size or to a suitable particle size distribution before a flotation process, for example, at a particle size less than 300 pm or less than 100 pm. At the same time, a fraction of fine particles is obtained, which have an average particle size of less than 10 pm. In order to produce slurries comprising particles having a range of particle sizes suitable for flotation, a feed of ground ore is conducted to a classification circuit 12 comprising several classifiers such as cyclones and magnetic separators (not shown in the figures), as is commonly known in the sector. For example, a cyclone separates ore particles based on their density, directing the coarse particles toward the receiver, which can then be further sorted in a magnetic separator to separate some of the iron-containing ore particles, such as magnetite, from the feed. of sludge to the flotation circuit. Briefly, classification circuit 12 separates ground ore at the overflow of classifier 121, to be treated in an ore flotation circuit 13, and slag 122 is removed from waterline 10. Classification circuit 12 It may be arranged in any suitable manner according to the raw material of the ore and the flotation process, as is evident to one skilled in the art.

The float line 10 further comprises a mineral flotation circuit 13 to treat the overflow of the classifier 121 as feed of mineral particles containing valuable material suspended in the sludge. Before conveying the classifier overflow 121 to the mineral flotation circuit 13, it may be conditioned and/or otherwise pretreated, in any suitable conventional manner, to prepare the classifier overflow 121 for a slurry feed, for example by adding flotation chemicals.

The mineral flotation circuit 13 comprises a raw portion 13a for separation of the sludge feed into a raw overflow 131a of recovered valuable material and a reject raw decant 132a. The mineral flotation circuit further comprises a cleaner portion 13b arranged to receive a raw overflow 131a of the raw portion 13a as a sludge feed, for separation of the sludge into a cleaner overflow 131b of recovered valuable material. , and a cleaner slop 132b which is arranged to flow back to the cruder part 13a as a sludge feed, to be treated again in a conventional manner.

The flotation plant 1 further comprises a process water circuit 20 for treating the settling and/or overflow 121, 122, 131b, 132a of the waterline 10. The process water circuit 20 comprises a solid separator -gravity liquid 21 to dehydrate the decant and/or overflow 121, 122, 131b, 132a of the waterline 10 of minerals, to separate the sediment 212 from the supernatant 211. The supernatant 211 comprises at least water and fine particles not recovered containing valuable material. The gravity solid-liquid separator 21 may be of any suitable type known in the art and selected in accordance with the process requirements of the flotation plant 1 and/or the waterline 10, as is evident for a skilled. The gravity solid-liquid separator 21 may be, for example, a thickener such as a waste thickener (conventional thickener, high speed thickener, high concentration thickener or paste thickener), or a clarifier.

The process water circuit 20 also comprises a recovery water tank 25 for collecting process water 500, which comprises the overflow and/or decanting of the mineral waterline 10. There may also be another recovery water tank 26 to collect and/or store purified process water 232, 232a. 232b before recirculating it back to waterline 10 as process water 500 (see Figures 2 and 3).

The solid-liquid gravity separator 21 may be a first solid-liquid gravity separator 21a arranged to dewater the decant of the classifier 122 to separate the first sediment 212a from the supernatant 211a, which comprises at least water and unrecovered fine particles containing material. valuable. The first sediment 212a is arranged to flow to a filtration circuit (not shown in the figures) for the recovery of valuable material, as is done conventionally, and the supernatant 211a is configured to be collected in the recovery water tank as collected process water. The first sediment 212a is extracted from the flotation plant 1 as waste, and treated in a conventional manner, for example, in a waste impoundment (not shown in the figures).

Alternatively or additionally, the solid-liquid gravity separator 21 may be a second solid-liquid gravity separator 21b arranged to dewater the overflow of the classifier 121 to separate the second sediment 212b from the supernatant 211b, which contains at least water and non-fine particles. recovered containing valuable material. The second sediment 212b is arranged to flow into the mineral flotation circuit 13 as a sludge feed, and the supernatant 211b is configured to be collected in the recovery water tank 25 as collected process water 500.

Alternatively or additionally, the solid-liquid gravity separator 21 may be a third solid-liquid gravity separator 21c arranged to dewater the cleaner overflow 131b of the mineral flotation circuit 13 to separate the third sediment 212c from the supernatant 211c, comprising at least water, unrecovered fine particles containing valuable material. The supernatant 211c of the third solid-liquid gravity separator 21c may further comprise microbes and residual flotation chemicals and other soluble or colloidal substances, as carryover from the waterline 10. The supernatant 211c is configured to be collected in the recovery water tank 25 as collected process water 500. The third sediment 212c is recovered as concentrate and treated conventionally to recover the desired valuable material.

Alternatively or additionally, the solid-liquid gravity separator 21 may be a fourth solid-liquid gravity separator 21d arranged to dewater the raw slop 132a of the mineral flotation circuit 13 to separate the fourth sediment 212d from the supernatant 211d, which comprises at least water and unrecovered fine particles containing valuable material. The supernatant 211d may further comprise microbes and residual flotation chemicals and other soluble or colloidal substances as a remnant of the waterline 10. The supernatant 211d is configured to be collected in the recovery water tank 25 as process water. collection 500. The fourth sediment 212 is extracted from flotation plant 1 as waste.

The process water circuit 20 comprises a washing flotation unit 23 employing flotation gas bubbles, at least 90% of which have a size between 0.2 and 250 pm, operatively connected to the solid-liquid separator. by gravity 21 to receive the supernatant 211 before being conveyed to the recovery water tank 25. The washing flotation unit 23 is arranged 1) to collect at least unrecovered fine particles containing valuable material; 2) separating fine particles containing valuable material from the supernatant in the wash flotation overflow 231 as recovered valuable material; and 3) obtaining purified process water 232 as decanted from the wash flotation, configured to be recirculated to the mineral float line 10, or collected in the recovery water tank 25 as collected process water 500.

The washing flotation unit 23 may be a first washing flotation unit 23a employing flotation gas bubbles, at least 90% of which have a size between 0.2 and 250 pm, operatively connected to the first separator. gravity solid-liquid 21a to receive the supernatant 211a, and arranged 1) to collect at least unrecovered fine particles containing valuable material; 2) separating fine particles containing valuable material from the supernatant in the overflow of the washing flotation 231a as recovered valuable material; and 3) obtaining purified process water 232a as wash flotation slop, configured to be recirculated in the mineral float line 10, or collected in the recovery water tank 25 as collected process water 500.

Alternatively or additionally, the washing flotation unit 23 may be a second washing flotation unit 23 employing flotation gas bubbles of which at least 90% have a size between 0.2 and 250 pm, operatively connected to the recovery water tank 25 to receive the collected process water 500, and arranged 1) to collect at least unrecovered fine particles containing valuable material, 2) to separate fine particles containing valuable material from the process water collected in the overflow from the wash flotation 231b as recovered valuable material, and 3) to obtain purified process water 232b as decant from the wash flotation; the purified process water being configured to be recirculated to the mineral waterline 10.

Depending on the configuration of the flotation plant 1, the process water circuit 20 may therefore comprise 1 to 4 solid-liquid gravity separators 21. Depending on their location within the flotation plant, the separators solid-liquid gravity 21, 21a, 21b, 21c, 21d can be chosen from a list comprising: a sludge thickener, a flotation thickener, a valuable material concentrate thickener, a waste thickener.

In order to recover fine particles containing valuable material from the overflow and/or decantation of the waterline 10, the supernatant 211a, 211b, 211c, 211d of a solid-liquid gravity separator or several solid-liquid gravity separators Liquid 21a, 21b, 21c, 21d can first be collected in the recovery water tank 25 and led to the second washing flotation unit 23b (Figure 3). Alternatively or additionally, the supernatant 211a of the first solid-liquid gravity separator 21a can be first led to the first washing flotation unit 23a, and then taken to the recovery water tank 25, or recirculated back to the line. flotation 10 at some suitable point on the waterline 10, for example as dilution water, that is, the configuration may be a combination of the alternatives shown in Figures 2 and 3.

The washing flotation units 23, 23a, 23b use flotation gas to float the particles collected by the collector chemicals. Specifically, flotation in the washing flotation units 23, 23a, 23b is performed using microbubbles or flotation gas bubbles having a particular size range. In the washing flotation and in the washing flotation units 23, 23a, 23b according to the invention, at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm. The scrubbing flotation may employ dissolved gas flotation (DAF), and the scrubbing flotation units 23, 23a, 23b may be a DAF unit. Other procedures can also be used to carry out flotation with smaller flotation gas bubbles, such as double-layer electric flotation or membrane flotation.

Additionally, the process water circuit 20 may comprise a filter unit 24, to remove microbes and chemicals that promote microbiological growth, or to remove any other unwanted chemicals from the purified process water (see Figure 2). The filter unit 24 may be of any type known in the art. In one embodiment, the filter unit 24 comprises a ceramic filter or several ceramic filters. The filter unit may be located after a washing flotation unit 23, or after a recovery water tank 25, 26, so that the purified process water is filtered before being recirculated back to the line. flotation 10.

Additionally, the process water circuit 20 may comprise a separator overflow tank 22a directly after the solid-liquid gravity separator (see Figure 2). The supernatant is taken to the separator overflow tank 22a before being directed to the washing flotation unit, for example, to control the volumetric flow into the washing flotation unit.

Furthermore, additionally or alternatively, the process water circuit 20 may comprise a mixing unit 22b (see Figure 2) after the solid-liquid gravity separator, or after the separator overflow tank 22a, if one is used. The mixing unit 22b may be of any type known in the art, arranged to allow the addition of the desired chemicals such as coagulants and/or flocculants and the treatment of the supernatant by chemical conditioning, so that at least the fine particles containing valuable material can be flocculated before taking the supernatant to the washing flotation unit. Likewise, other compounds, such as for example soluble SiO<2>, can also be flocculated in the form of solid particles and, in this way, can be subsequently removed from the purified process water. This may be necessary, if the supernatant does not contain a sufficient amount of waste chemicals from the collector as carryover from the waterline 10, to ensure sufficient flocculation of fine particles comprising valuable material in the washing flotation unit, or to ensure the creation of sufficiently large flocs in the washing flotation unit. Both the separator overflow tank 22a and the mixing unit 22b can further be used to adjust the temperature and/or pH of the supernatant, if desired, to prepare the supernatant for washing flotation.

The process water circuit 20 may further comprise a filter unit 24 to remove microbes and chemicals that promote microbiological growth, or to remove any other unwanted chemicals from the purified process water, or from the process water 500. which is recirculated to the waterline 10 (see Figure 2). The filter unit 24 may be of any type known in the art. In one embodiment, the filter unit 24 comprises a ceramic filter or several ceramic filters. In the procedure for treating process water from flotation facility 1, the following steps are carried out.

The settling and/or overflow from a mineral waterline 10 is treated in a process water circuit 20 comprising a solid-liquid gravity separator 21 to dewater the settling and/or overflow from the waterline 10. of minerals, to separate the sediment 212 from the supernatant 211, which comprises at least water and fine particles containing valuable material. The process water circuit 20 further comprises a recovery water tank 25 for collecting and/or storing process water 500, which comprises overflow and/or decanting of the mineral waterline 10.

Before carrying the supernatant 211 from the solid-liquid gravity separator 21 to the recovery water tank 25, the supernatant 211 is subjected to a wash flotation, in which at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a washing flotation unit 23. In the washing flotation, at least the unrecovered fine particles containing valuable material are recovered from the supernatant 211. The fine particles containing valuable material They are separated from the supernatant 211 at the wash flotation overflow 231 as recovered or concentrated valuable material, and from there, they are conveyed to a conventional process step to recover the valuable material (such as a filtration step). The purified process water 232 is obtained as decant from the washing flotation. The purified process water 232 is recirculated to the mineral waterline 10, at any suitable or required position of the mineral waterline 10, for example, as dilution water. Alternatively, the purified process water may be first collected in the recovery water tank 25 as collected process water 500 and then recirculated in the mineral waterline 10, or at any other stage of the recovery process. flotation plant 1.

In one embodiment, the process water circuit 20 comprises a first solid-liquid gravity separator 21a for dewatering the decant of the classifier 122 to separate the first sediment 212a from the supernatant 211a, which comprises at least water and unrecovered fine particles containing valuable material. The first solid-liquid gravity separator 21a may be a sludge thickener. The first sediment may be collected as a concentrate and arranged to flow to a filter circuit 14 for recovery of valuable material. The supernatant is collected in recovery water tank 25 as collected process water 500.

Before carrying the supernatant 211a from the first solid-liquid gravity separator 21a to the recovery water tank 25, the supernatant 211a is subjected to a wash flotation, in which at least 90% of the flotation gas bubbles They have a size between 0.2 and 250 pm, in a first washing flotation unit 23a, 1) to collect at least unrecovered fine particles containing valuable material; 2) to separate fine particles containing valuable material from the supernatant in the wash flotation overflow 231a as recovered valuable material; and 3) to obtain purified process water 232a as decant from the washing flotation. The purified process water 232a is recirculated to the mineral waterline 10, or collected in the recovery water tank 25 as collected process water 500.

Alternatively or additionally, the process water circuit 20 may comprise a second gravity solid-liquid separator 21b to dewater the overflow of the classifier 121 to separate the second sediment 212b from the supernatant 211b, which comprises at least water and unrecovered fine particles that They contain valuable material. The second solid-liquid gravity separator 21b may be a flotation thickening agent. The second sediment 212b is conveyed to the mineral flotation circuit 13 as sludge feed. The supernatant 211b is collected in the recovery water tank 25 as collected process water 500.

Alternatively or additionally, the process water circuit 20 may comprise a third gravity solid-liquid separator 21c to dewater the cleaner overflow 131b of the flotation circuit 13 to separate the third sediment 212c from the supernatant 211c, which contains at least water and unrecovered fine particles containing valuable material. The third gravity solid-liquid separator 21c may be a concentrated thickener of valuable material, for example, a high-rate thickener. The supernatant 211c may further comprise residual flotation chemicals, colloidal and soluble compounds, and microbes. The supernatant 211c is collected in the recovery water tank 25 as collected process water 500. The third sediment 212c can be collected as a concentrate and conducted to further treatment to recover the target valuable material, for example, in a filtering step. (not shown in the figures).

Alternatively or additionally, the process water circuit 20 may comprise a fourth gravity solid-liquid separator 21d for dewatering the raw slop 132a from the flotation circuit 13 to separate the fourth sediment 212d from the supernatant 211d, which comprises at least water and unrecovered fine particles containing valuable material. The fourth solid-liquid separator 21d may be a waste thickening agent. The supernatant 211d may further comprise residual flotation chemicals, colloidal and soluble compounds, and microbes. The supernatant 211d is collected in the recovery water tank 25 as collected process water 500. The fourth sediment 212d can be extracted from the flotation plant 1 as waste and treated accordingly, for example, in a waste reservoir.

In one embodiment, before recirculating one or more supernatants 211a, 211b, 211c, 211 d as collected process water 500 from the recovery water tank 25, to the mineral waterline 10, the collected process water 500 is subjected to a washing flotation, in which at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a second washing flotation unit 23b, 1) to collect at least particles unrecovered fines containing valuable material, 2) to separate fine particles containing valuable material from the process water collected in the washing flotation overflow 231b as recovered valuable material, and 3) to obtain purified process water 232b as decantation of the washing flotation; This purified process water can then be recirculated to the mineral waterline 10.

The scrubbing flotation may be a dissolved gas flotation (DAF), that is, the scrubbing flotation unit 23 may be a DAF unit.

Depending on the configuration of the flotation plant 1, the process water circuit 20 may therefore comprise 1 to 4 solid-liquid gravity separators 21. To recover fine particles containing valuable material from overflow and/or settling From the waterline 10, the supernatant 211a, 211b, 211c, 211d of a gravity liquid-solid separator or several gravity liquid-solid separators 21a, 21b, 21c, 21d can be collected first in the tank 25 of recovery water, and taken to the second washing flotation unit 23b (Figure 3).

Alternatively or additionally, the supernatant 211a of the first solid-liquid gravity separator 21a can be first led to the first washing flotation unit 23a, and then taken to the recovery water tank 25, or recirculated back to the waterline 10 at some suitable point on the waterline 10, for example, as dilution water, that is, the configuration may be a combination of the alternatives shown in Figures 2 and 3.

Before the purified process water is recirculated in the mineral waterline 10, it may be collected and/or stored in a second recovery water tank 26.

Furthermore, before recirculating purified process water in the mineral waterline 10, or before recirculating process water 500 from a recovery water tank 25, 26 in the mineral waterline 10, the water may be subjected to a filtering step in a filtration unit 24, to remove microbes and chemicals that promote microbiological growth, or to remove any other unwanted chemicals from the purified process water, or from process water 500 that is recirculated in the mineral waterline 10 (see figure 2).

Before carrying the overflow and/or decant 121, 122, 131b, 132a from the mineral waterline 10 to the solid-liquid gravity separator 21, 21a, 21b, 21c, 21d, the concentration of the overflow and/or the decant 121, 122, 131b, 132a can be adjusted to be between 0.5 and 15% by weight, in any conventional manner, for example using recirculated process water 500 as dilution water. Furthermore, by this, the turbulent flow of overflow and/or decantation from the mineral waterline 10 can be adjusted to be a laminar flow as it is conducted to the solid-liquid gravity separator 21, 21a, 21b, 21c, 21d .

For example, in the fourth solid-liquid gravity separator 21d ("waste thickener"), the incoming slop 132a may have a concentration typically between 35 and 45% by weight. By reducing the concentration from 0.5 to 15% by weight by adding process water 500, better sedimentation of solid particles can be achieved under laminar conditions, since ideal conditions are created for a fine particle washing step. . In general, fine particles of less than 10 pm particle size will remain in the water in the supernatant rather than settling to the bottom of the solid-liquid gravity separator as sediment. A person skilled in the art can adjust the appropriate concentration with information on the size and density range of the settling material and/or the incoming overflow with respect to the upward or surface loading rate of the solid-liquid gravity separator.

The residence time of the overflow and/or decantation 121, 122, 131b, 132a in a solid-liquid gravity separator 21, 21a, 21b, 21c, 21d is less than 10 hours. The residence time may be between 0.5 and 8 hours, for example 1 hour; 2.25 hours; 3.5 hours; 4 hours; 5.75 hours; or 6.5 hours. The temperature of the supernatant 211, 211a, 211b, 211c, 211d can be adjusted between 2 and 60 ° C, and the pH can be adjusted between 6 and 12 before taking it to a washing flotation unit 23, 23a, 23b. The pH may be, or may be adjusted, for example, to 7; or 7.3; or 7.5; u 8; or 9.25. The temperature and pH of the supernatant 211, 211a, 211b, 211c, 211d can be adjusted to optimize the washing flotation in the washing flotation unit 23, 23a, 23b, or the above process steps can make the temperature and /or the pH of the supernatant show certain values. The properties of the supernatant 211,211a, 211b, 211c, 211d mentioned above can be adjusted separately in the overflow tank of the separator 22a.

Depending on the type of raw material or ore treated in the flotation plant 1, a significant amount of fine particles containing valuable material, not recovered in the mineral waterline 10, can be recovered from the supernatant 211, 211a, 211b , 211c, 211d of a solid-liquid gravity separator (21, 21a, 21b, 21c, 21d). In one embodiment, at least 40% of the fine particles containing valuable material are recovered. In some cases, up to 90% of fine particles containing valuable material can be recovered.

After the wash flotation, the wash flotation overflow 231, 231a, 231b is removed as concentrate and the purified process water 232, 232a, 232b is recirculated to the mineral flotation circuit 10. Before recirculating the purified process water 231 to the mineral flotation circuit 10, it can be subjected to a filtering step to eliminate chemicals that promote microbiological growth or to eliminate other unwanted or harmful chemical compounds. In the filtration step, a filter unit 24 comprising a ceramic filter may be used.

The hardness of the purified process water 232, 232a, 232b may not be affected by the process water circuit 20 and/or the process for treating the process water, that is, the hardness of the settling and/or overflow water 121, 122, 131b, 132a of mineral waterline 10 is substantially the same as the water hardness of purified process water 232, 232a, 232b, or process water 500, recirculated to mineral waterline 10. minerals.

In a further step of the procedure, before taking the supernatant 211, 211a, 211b, 211c, 211d from a solid-liquid gravity separator 21, 21a, 21b, 21c, 21d to the washing flotation, the supernatant can be led to a separator overflow tank 22a. Additionally or alternatively, before taking the supernatant 211, 211a, 211b, 211c, 211d from a solid-liquid gravity separator 21, 21a, 21b, 21c, 21d to the washing flotation, the supernatant can be taken to the washing flotation unit. mixture 22b, to chemically condition the supernatant by adding a coagulant and/or a flocculant to flocculate at least the fine particles containing valuable material in the supernatant. The coagulant can be chosen from a group comprising: inorganic coagulants, aluminum salts, iron salts and organic coagulants.

A possible inorganic coagulant is polyaluminum chloride (PAC). An inorganic coagulant can be added to the supernatant 211, 211a, 211b, 211c, 211d in the mixing unit 22b in an amount between 1 and 2,000 ppm, for example, in an amount of 5 ppm, 10 ppm, 25 ppm, 50 ppm, 75 ppm, 150 ppm, 225 ppm, 350 ppm or 400 ppm. In one embodiment, 100 ppm of<p>A<c> is added. An organic coagulant can be added to the supernatant 211, 211a, 211b, 211c, 211d in an amount between 5 and 200 ppm.

Alternatively or additionally, the supernatant 211, 211a, 211b, 211c, 211d can be conditioned in the mixing unit 22b by adding a flocculant to further help recover fine particles containing valuable material from the supernatant 211, 211a, 211b, 211c, 211d, flocculating them. . For example, natural flocculants such as starch or modified starch, or polysaccharides can be used. For example, synthetic flocculants can be used. Synthetic flocculants can have different charges. Examples of synthetic flocculants are: high molecular weight flocculants (more than 500,000), such as polyacrylamides (negatively or positively charged, or neutral), or Mannich products (positively charged); and low molecular weight flocculants (less than 500,000), such as polyamines (positively charged), polyepiamine (positively charged), polyDADMAC (positively charged), poly(ethylene)imines (positively charged) or polyethylene oxide (neutral).

A flocculant can be added in an amount between 1 and 100 ppm, for example in an amount of 1.25 ppm, 1.75 ppm, 2.25 ppm, 7.5 ppm or 12.25 ppm. In one embodiment, 2 ppm of a flocculant is added.

The use of the installation according to the above invention can be used in a flotation plant 1 intended to recover valuable material from ores having a density of less than 4 g/cm3, preferably between 2.4 and 3.2 g/cm3 . For example, spodumene has a density of 3.11 g/cm3. In one embodiment, the valuable material is Li. In one embodiment, the valuable material is Pt. In one embodiment, the raw material from flotation plant 1 is spodumene ore, from which lithium is intended to be recovered. In one embodiment, PGM ores or other sources of Pt are used as raw material for flotation plant 1, intended to recover Pt.

Claims (37)

1. Procedure for treating the process water of a flotation plant (1) for the recovery of a valuable material, the flotation plant comprising a mineral flotation line (10), the mineral flotation line comprising: - a grinding mill (11); - a classification circuit (12), to classify the feed of ground ores (110) from the crushing mill in overflow from the classifier (121) and in decantation from the classifier (122); and - a mineral flotation circuit (13), to treat the overflow of the classifier as a feed of ore particles containing valuable material suspended in sludge, the flotation circuit comprising a rougher part (13a) for separating the feed of the sludge in a raw overflow (131a) of recovered valuable material and a reject raw decant (132a), and a cleaner part (13b), arranged to receive the raw overflow (131a) of the raw part as a sludge feed for separating the sludge into a cleaner overflow (131b) of recovered valuable material and a cleaner decant (132b) arranged to flow back to the raw part as a sludge feed, The flotation plant (1) also comprises a process water circuit (20) for treating the settling and/or overflow of the mineral float line, the process water circuit comprising a solid-liquid separator for gravity (21) to dewater the decant and/or waterline overflow of minerals to separate the sediment (212) from the supernatant (211), which comprises at least water and unrecovered fine particles containing valuable material; and a recovery water tank (25), to collect process water (500) that comprises overflow and/or decantation of the waterline (10) of minerals, characterized in that, before leading the supernatant (211) from the solid-liquid separator by gravity (21) to the recovery water tank (25), the supernatant is subjected to a washing flotation, in which at least the 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a washing flotation unit (23) to collect at least unrecovered fine particles containing valuable material; to separate fine particles containing valuable material from the supernatant in the wash flotation overflow (231) as recovered valuable material; and to obtain purified process water (232) as decanted from the washing flotation; and because the purified process water is recirculated to the mineral waterline (10) or collected in the recovery water tank (25) as collected process water (500). 2. Procedure, according to claim 1, characterized in that the process water circuit (20) comprises a first solid-liquid gravity separator (21a) to dehydrate the decant of the classifier (122) to separate the first sediment (212a) from the supernatant (211a), comprising at least water and unrecovered fine particles containing valuable material; the first sediment being arranged to flow towards the filter circuit (14) for the recovery of valuable material and the supernatant collected in the recovery water tank (25) as collected process water (500). 3. Procedure, according to claim 2, characterized in that before taking the supernatant (211a) from the first solid-liquid gravity separator (21a) to the recovery water tank (25), the supernatant is subjected to washing flotation , in which at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a first washing flotation unit (23a) to collect at least unrecovered fine particles containing material valuable; to separate fine particles containing valuable material from the supernatant in the wash flotation overflow (231a) as recovered valuable material; and to obtain purified process water (232a) as decanted from the washing flotation; and because the purified process water is recirculated to the mineral waterline (10) or is collected in the recovery water tank (25) as collected process water (500). 4. Procedure, according to any of claims 1 to 3, characterized in that the process water circuit (20) comprises a second solid-liquid gravity separator (21b) to dehydrate the overflow of the classifier (121) to separate the second sediment. (212b) of the supernatant (211b), which comprises at least water and unrecovered fine particles containing valuable material; the second sediment (212b) being conveyed to the mineral flotation circuit (13) as a sludge feed; and the supernatant (211b) being collected in the recovery water tank (25) as collected process water (500). 5. Procedure, according to any of claims 1 to 4, characterized in that the process water circuit (20) comprises a third solid-liquid separator by gravity (21c) to dehydrate the cleaner overflow (131b) of the flotation circuit ( 13) to separate the third sediment (212c) from the supernatant (211c), which contains at least water and unrecovered fine particles containing valuable material; the supernatant (211c) being collected in the recovery water tank (25) as collected process water (500). 6. Procedure, according to any of claims 1 to 5, characterized in that the process water circuit (20) comprises a fourth solid-liquid gravity separator (21d) to dehydrate the raw decant (132a) of the flotation circuit ( 13) to separate the fourth sediment (212d) from the supernatant (211d), which comprises at least water and unrecovered fine particles comprising valuable material; the supernatant (211d) being collected in the recovery water tank (25) as collected process water (500). 7. Procedure, according to any of claims 1 to 6, characterized in that before recirculating the collected process water (500) from the recovery water tank (50) to the mineral waterline (10), the water from the The collected process is subjected to a washing flotation, in which at least 90% of the flotation gas bubbles have a size between 0.2 and 250 pm, in a second washing flotation unit (23b) to collect at least unrecovered fine particles containing valuable material, to separate fine particles containing valuable material from the process water collected in the overflow of the washing flotation (231b) as recovered valuable material, and to obtain purified process water (232b) as decanting of washing flotation; and because the purified process water is recirculated to the mineral waterline (10). 8. Procedure, according to any of claims 1 to 7, characterized in that before carrying the overflow and/or decanting of the waterline (10) of minerals to a solid-liquid separator by gravity (21, 21a, 21b, 21c, 21d), the concentration of the overflow and/or the settling is adjusted between 0.5 and 15% by weight. 9. Procedure, according to claim 8, characterized in that the turbulent flow of the overflow and/or decantation from the waterline (10) of minerals is adjusted to a laminar flow when it is conducted to the solid-liquid separator by gravity (21, 21a, 21b, 21c, 21d). 10. Procedure according to any of claims 1 to 9, characterized in that at least 40% of the fine particles containing valuable material, not recovered in the mineral waterline (10), are recovered from the supernatant (211, 211a). , 211b, 211c, 211d) of a solid-liquid gravity separator (21,21a, 21b, 21c, 21d). 11. Procedure, according to any of claims 1 to 10, characterized in that the permanence time of the overflow and/or decantation of the waterline (10) of minerals in the solid-liquid gravity separator (21,21a, 21b , 21c, 21d) is less than 10 hours, preferably between 0.5 and 8 hours. 12. Procedure, according to any of claims 1 to 11, characterized in that before carrying the supernatant (211,211a, 211b, 211c, 211 d) from a solid-liquid gravity separator (21,21a, 21b, 21c, 21d) To a washing flotation, the supernatant is taken to an overflow tank of the separator (22a). 13. Procedure, according to any of claims 1 to 12, characterized in that before carrying the supernatant (211,211a, 211b, 211c, 211 d) from a solid-liquid gravity separator (21,21a, 21b, 21c, 21d) In a washing flotation, the supernatant is conducted to the mixing unit (22b) to chemically condition the supernatant by adding a coagulant and/or a flocculant to flocculate at least fine particles containing valuable material in the supernatant. 14. Procedure, according to claim 13, characterized in that the coagulant is chosen from a group that includes: inorganic collector, aluminum salts, iron salts, organic coagulants. 15. Procedure, according to claim 13 or 14, characterized in that a coagulant is added to the supernatant (211,211a, 211b, 211c, 211d) in an amount between 1 and 2,000 ppm. 16. Procedure, according to any of claims 13 to 15, characterized in that the flocculant is chosen from a group that includes: natural polymers, synthetic flocculants. 17. Procedure, according to any of claims 13 to 16, characterized in that a flocculant is added to the supernatant (211,211a, 211b, 211c, 211 d) in an amount between 1 and 100 ppm. 18. Procedure, according to any of claims 1 to 17, characterized in that the temperature of the supernatant (211,211a, 211b, 211c, 211d) is adjusted between 2 and 60 ° C before taking it to a washing flotation unit (23, 23a, 23b). 19. Procedure, according to any of claims 1 to 18, characterized in that the pH of the supernatant is adjusted between 6 and 12 before taking it to a washing flotation unit (23, 23a, 23b). 20. Method according to any of claims 1 to 19, characterized in that the washing flotation unit (23, 23a, 23b, 23c) is a dissolved gas flotation (DAF) unit. 21. Procedure, according to any of claims 1 to 20, characterized in that the valuable material is Li. 22. Method according to any of claims 1 to 20, characterized in that the valuable material is Pt. 23. Installation for treating the process water of a flotation plant (1) for the recovery of a valuable material, the flotation plant comprising a mineral flotation line (10), the mineral flotation line comprising: - a grinding mill (11); - a classification circuit (12), to classify the feed of ground ores from the mill in an overflow of the classifier (121) and a decantation of the classifier (122); and - a mineral flotation circuit (13), for treating mineral particles containing valuable material suspended in the sludge, the mineral flotation circuit comprising a raw part (13a) for separating the sludge fed into an overflow raw material (131a) of recovered valuable material and a raw decant (132a) of rejection, and a cleaner part (13b) arranged to receive the raw overflow (131a) of the rawer part as a sludge feed, to separating the sludge into a cleaner overflow (131b) of recovered valuable material and a cleaner slop (132b) arranged to flow back to the cruder part as a sludge feed, the flotation plant (1) also comprising a process water circuit (20), to treat the settling and/or overflow of the mineral flotation line, the process water treatment circuit comprising a solid-liquid separator. by gravity (21), arranged to dewater the decant and/or the waterline overflow of minerals to separate the sediment (212) from the supernatant (211), which comprises at least water and unrecovered fine particles containing valuable material ; and a recovery water tank (25) to collect process water (500), which comprises overflow and/or decanting of the mineral waterline, characterized in that the water treatment circuit (20) further comprises a washing flotation unit (23) that uses flotation gas bubbles, of which at least 90% have a size between 0.2 and 250 pm, operatively connected to the solid-liquid gravity separator (21) to receive the supernatant (211) before being conveyed to the recovery water tank, and arranged to collect at least fine unrecovered particles containing valuable material; to separate fine particles containing valuable material from the supernatant in the wash flotation overflow (231) as recovered valuable material; and to obtain purified process water (232) as decanted from the washing flotation configured to be recirculated to the mineral float line (10) or collected in the recovery water tank (25) as collected process water (500 ). 24. Installation, according to claim 23, characterized in that the process water circuit (20) comprises a first solid-liquid gravity separator (21a) arranged to dehydrate the decant of the classifier (122) to separate the first sediment (212a). from the supernatant (211 a), which comprises at least water and unrecovered fine particles containing valuable material; the first sediment being arranged to flow towards the filter circuit (14) for the recovery of valuable material; the supernatant being configured to be collected in the recovery water tank (25) as collected process water (500). 25. Installation according to claim 24, characterized in that the water treatment circuit (20) comprises a first washing flotation unit (23a) that uses flotation gas bubbles of which at least 90% have a size comprised between 0.2 and 250 pm, operatively connected to the first solid-liquid gravity separator (21a) to receive the supernatant (211a), and being arranged to collect at least unrecovered fine particles containing valuable material; to separate fine particles containing valuable material from the supernatant in the wash flotation overflow (231a) as recovered valuable material; and to obtain purified process water (232a) as decant from the washing flotation configured to be recirculated in the mineral float line (10), or collected in the recovery water tank (25) as collected process water (232a). 500). 26. Installation, according to any of claims 23 to 25, characterized in that the process water circuit (20) comprises a second solid-liquid gravity separator (21b) arranged to dehydrate the overflow of the classifier (121) to separate the second sediment (212b) from the supernatant (211b), comprising at least water and unrecovered fine particles containing valuable material; the second sediment (212b) being arranged to flow towards the mineral flotation circuit (13) as a sludge feed; and the supernatant (211b) being configured to be collected in the recovery water tank (25) as collected process water (500). 27. Installation, according to any of claims 23 to 26, characterized in that the process water circuit (20) comprises a third solid-liquid gravity separator (21c) arranged to dehydrate the cleanest overflow (131b) of the circuit (13). ) mineral flotation to separate a third sediment (212c) from the supernatant (211c), which comprises at least water and unrecovered fine particles containing valuable material; the supernatant (211c) being configured to be collected in the recovery water tank (25) as collected process water (500). 28. Installation, according to any of claims 23 to 27, characterized in that the process water circuit (20) comprises a fourth solid-liquid gravity separator (21d) arranged to dehydrate the raw decant (132a) of the flotation circuit. of minerals (13) to separate the fourth sediment (212d) from the supernatant (211d), which comprises at least water and unrecovered fine particles containing valuable material; the supernatant (211d) being configured to be collected in the recovery water tank (25) as collected process water (500). 29. Installation, according to any of claims 23 to 28, characterized in that the process water circuit (20) also comprises a second washing flotation unit (23b) that uses flotation gas bubbles, of which as At least 90% has a size between 0.2 and 250 pm, operatively connected to the recovery water tank (25) to receive collected process water (500), and arranged to collect at least fine unrecovered particles containing material. valuable, to separate fine particles containing valuable material from the process water collected in the overflow of the washing flotation (231b) as recovered valuable material, and to obtain purified process water (232b) as decanted from the washing flotation; the purified process water being configured to be recirculated in the mineral waterline (10). 30. Installation, according to any of claims 23 to 29, characterized in that the process water circuit (20) comprises an overflow tank of the separator (22a) in which the supernatant (211, 211a, 211b, 211c, 211d) of a solid-liquid gravity separator (21, 21a, 21b, 21c, 21d) is configured to flow before being taken to the washing flotation. 31. Installation, according to any of claims 23 to 30, characterized in that the process water circuit (20) also comprises a mixing unit (22b) in which the supernatant (211,211a, 211b, 211c, 211d) of the solid-liquid gravity separator (21, 21a, 21b, 21c, 21d) is configured to flow before being taken to the washing flotation, the mixing unit being arranged to chemically condition the supernatant to flocculate at least fine particles that contain valuable material in the supernatant. 32. Installation according to any of claims 23 to 31, characterized in that the washing flotation unit (23, 23a, 23b, 23c) is a dissolved gas flotation unit (DAF). 33. Use of the installation according to any of claims 23 to 32 to recover valuable material from an ore having a density of less than 4 g/cm3, preferably between 2.4 and 3.2 g/cm3. 34. Use according to claim 33, to recover Li. 35. Use according to claim 34, to recover Li from spodumene. 36. Use according to claim 33, to recover Pt. 37. Use according to claim 36 to recover Pt from a PGM mineral.